Method of forming a tobacco product of increased wet strength



A. B. CLARKE July 13, 1965 METHOD OF FORMING A TOBACCO PRODUCT OF INCREASED WET STRENGTH Filed Oct. 4, 1962 80 I00 DRYING TEMPERATURE C 5 z m w m United States Patent 3,194,245 METHCD 0F FQRMING A TOBACCG PRODUCT 0F INCREASED WET STRENGTH Allan 3. Clarke, Midlothian, Va, assignor to Philip Morris incorporated, New York, N.Y., a corporation of Virginia Filed Got. 4, 1962, Ser. No. 230,399 4 Claims. (Cl. 131-140) This application is a continuation-impart of application Serial No. 839,658, which was filed on September 14, 1959, now abandoned.

The present invention is concerned with a method of making a reconstituted tobacco product. The method consists of a series of operations and specified conditions whereby common .tobacco by-products such as stems and tobacco fines are formed into a sheet capable of being utilized in the normal manner of leaf tobacco as a smoking product. The sheet material produced may be cut o shredded similarly to the leaf parts and utilized for smoking either by itself or mixed with shredded leaf parts.

It has heretofore been proposed to grind up tobacco materials forming a wet slurry thereof, casting the slurry in the form of a film on a flat surface and drying the cast film. However, difficulties have been encountered in handling the film because of its physical weakness. Particularly the film lacked wet strength, which is a handicap because of the tendency of such films when cast and dried upon a flat surface to adhere to the surface requiring remoistening of the film to free it from the surface. Also the films had a tendency to soften and disintegrate when wetted. For example spraying the shredded product with a liquid such as fiavoringmaterials tended to reduce the shreds into a soft mass and destroy their crispness and resiliency. Alsothere was the liability of particles becoming soft and disintegrating when contacted by saliva in the smoking of a cigarette embodying the product. One remedy forthe difficulties was to add adhesivematerial to the slurry which gave added strength including wet strength to the product,

The present invention is based on the discovery that the strength and particularly the wet strength of the reconstituted tobacco product may be very materially increased by employing in the initial drying stage, after the free water has been removed, selected controlled temperature conditions within a critical range. The invention accordingly comprises the various steps and conditions which will be exemplified'in the method hereinafter disclosed and the scope of the invention will be indicated in the claims.

In the accompanying drawings:

FIG. 1 comprises a diagrammatic illustration of one form of apparatus for forming the film including the drying thereof within the temperature range to be described; and,

FIG. 2 is a plotted graph of tensile strengths of the sheet material dried at various temperatures.

The initial step preliminary to the film forming operations comprises the preparation of the tobacco slurry. The starting materials may comprise any part of the tobacco plant, that is imaged or aged leaf, stem or stalk portions or mixtures thereof, but the present method has particularly practical application in making use of tobacco parts which are commonly waste or at least not utilizable in the normal manner of the leaf portions. The starting material accordingly may comprise stem parts or tobacco leaf fines, or, as will now be described as a representative example, a mixture of stems and tobacco fines.

The method of preparing such a tobacco slurry preferably involves an initial separate treatment of the components. The stems are preferably cooked and beaten or refined. The treatment in general may be similar to the Patented July 13, 1965 ice pulp treatment in paper making. The leaf fines are preferably ground to further reduce the particle size such as to pass through an mesh screen. The two component products are then mixed together in a large excess of liquid and further ground or beaten if necessary to arrive at the desired state. Water will, in general, be the liquid which is employed, but other liquids capable of subsequent removal by evaporation may be employed.

It is important for the preparation of a satisfactory film, that the proportion of tobacco solids to liquid he in the range of from about 3 to about 8% by weight, with about 5% being preferred. The tobacco solids content may be about equal parts cooked pulp and raw ground fines; Desirably the slurry is soprepared, and particularly the treatment of the stems is carried on under controlled conditions, such as to result in a substantial proportion of tobacco ground to a gelatinous state and similarly a substantial proportion remaining as discrete fibers. For example the stem may be beaten to the condition such that one-third to one-half of the stem product may be recognizable under high magnification as definite discrete fibers. The slurry may, of course, contain also various additives such as glycerine or other humectants, non-volatile fiavo-rings and other materials common to smoking tobacco mixtures. As a whole, however, the solid constituents are predominantly and essentially tobacco.

FIG. 1 shows diagramamtically an apparatus and method for converting the slurry into a dried film. It includes primarily a movable fiat casting surface upon which the slurry is deposited and advanced through the drying zone. The coating surface as shown in FIG. 1 comprises a continuous metal band 10 preferably of stainless steel. The slurry may be deposited thereon by any standard means indicated in FIG. 1 as a supply box fl having an adjustable slit opening for delivering a film of slurry 12 onto the belt surface. The thickness of the layer will depend upon circumstances but as a representative example with a slurry containing about 5% solids the initial film, as regulated by the speed of the belt and size of slit opening, can be in the range of .050 to .125 inch. The film proceeds on the band ll} to the drying zone indicated in FIG. 1 as a forced draft oven 13 with a hot air intake 14- and exhaust 15. Conditions are selected such that the film 12a, as it emerges from the drying oven, is substantially free of water. However, in order to provide the outstanding results obtainable by means of the present invention, the way in which this result is accomplished involves two essential steps. In the first step, the film is heated to a temperature sufdciently high to drive off all the free water present in the film. The term free water, as employed herein, means all water present in the film which can be removed by bringing the Water to a temperature which corresponds to the boiling point of water. Thus, under atmospheric condi tions, the film will be subjected to a temperature of about C., whereby the free water is evaporated from the film. The second step, involves heating the thus-treated film until the film itself reaches a temperature which is at least C. and which is below 169 C. Preferably the film is heated until it reaches a temperature of Cd; 10 C.

The first step can be conducted in an oven at a temperature of from about 100 C. to 200 C. or even higher so long as the temperature of the film is no higher than 100 C. The duration of this step will depend on the thickness of the film, the moisture content of the film and other conditions of the film but will generally be between about 5 minutes and 2 hours. The end of this first step or heating period can be determined by measuring the temperature of the film during heating. For any temperature within the range of 1% to 290 C. to which the atmosphere in the oven is heated, the film will reach a temperatureplateau, which is :always considerably below,

100C; After this plateau has been reached, when the temperature'of the film begins to rise,- andparticularly when the temperature of thefilm reaches lCrOiC the'free Water can be considered to be driven off and-the first step can beconsidered completed. 7 V

The second step is then conducted by heating the film in an atmosphere maintained at a temperature'of from about 120 .C. up to 160 C. for a period of'time until the temperature of thefilm is at least 120 C. but below 160 'C; This can be done most readily in an'oven but can also be done employing hot drying rolls or other suit-* able means This time can readilybe determined by 'measuring :the .temperatureof the film by conventional: means an d will generallybe a'time 'of about 30 minutes The two drying-steps may be conducted in two separate ovens maintained at different temperatures or the film 7 can 'be passed through a single'oven having a temperature Preferably,-how ever, bothsteps are conductedin a'single oven,rsuch as oven 13, which is maintainedat; a temperature of from 120 C. up to 1603C. In this manncr,tbere is a smooth transition from step 1 to step :2

gradient.

slurry consisted of a pproxim sisted approximately'of; tobacco stems fines 46% and glycerine 4%. i

50 ,l tobaccojleaf samples for each of the selected.ternperatures'f'v 'The'iwct fapart. A transverse :band racrioss the 'stripgbetweemthe clamps was the'n ivvetted i by applying three-spaced. drops and. there is a minimum amountofequipment required a forthe two operations.- V It is of course necessary to remove and collect thedried film from the belt ill and preferably in the form of'a con-'- tinuous sheet for convenienthandling and storage. It is a characteristic, however, of dried films of the type and composition involved that, despite the highly. polished stir-- face ot'the stainless steel belt it the film adheres firmly -to the beltand canbe readily separated only by remoist- Accordingly, the film isl V sprayed with a liquid, which is preferably water, iniiSi ening to a. substantial degree.

return run as indicated at 18. The Wetting liquid may the :timeperiod thev tester was energized and the nongation andbreakage were. recorded on the graph papen attached tothe. tester. As stated above thevalue irithe I second-column of Table Aabelow is the tavera'ge,v offive.

tensile strength values recorded in theifbelow Table-A t comprise the average of: the five samplesatithe' respective temperatures indicated. y 4 i l V fr v The wet tensilestrength was determined as followsz;

, Thetobacco sheet was cut into stripsl inch wide by inchesfljong; Each strip wasplaced betweeniglampsonla standard Scott tester. withjthe clamps adjustedgtofl inch of distilled Water from'ran eye dropper,to 1lowedby:a 1 minute idle time .periodf This. scrvcd to" form. .a wet ba'ndabout'3 Tmm. j wider across {11116 strip. :At the end of samples at the re spective .dryirig temperaturea,

dyes. The degree of Wetting will vary in difierent casesbut=in general it is necessary to apply liquid to the extent of a moisture content in the range of about 20% to 40% in order-to be able to free the .i'ilm readily from the surface of the. traveling belt. In previous operationsgofsuch character ithas been found thatthe film, when remoist- 1 ened to the: degree necessary, commonly has inadequate strength for the manipulations in removing it fromthe that the operation, is accomplished Without difficulty,

The film proceeds fronrthe' spraying apparatus lti tor-pv wardly' to Where a doctor blade 19 servesto separate the film from the band ltl. SuitableF-rolls 2d and :21 vserve to support and direct the removed'film 12a in' its advance. Preferably, the removed film is redriedto a desired extent andaccordingly is directed. through a a drying; oven' 22 where the moisture content is reduced to about 12% to 15% and'is then woundon a collecting roll 23.

A large number of tests for wet tensile strength have been made on the film dried'at various temperatures and 1 16.2 is acurvc based on valuesthusrderived. V The samples for such tests'wer'e preparedasfollows:

A slurry of tobacco partswas made; First a quantity i of shredded tobacco stems was cooked with water in a pressure cooker'at 15 'lbs. pressure (approximately 240 i carrier band and-feeding it to a takeup roll, and it is due V to the critical drying operations of the present-invention F.) for one hour. Thiswas' refined in 'a beatertoa free.:

: mm on the,Schopper-Rieglerscale'of about 140, the mess I therefore comprising a mixture of gelatinousmaterial and r discrete-fibers each inat least a large. percentage. Q There was then added a quantity ottobacco leaf fines anda stituents for thirty-minutes in a Waring Blendorh The a small amountot glycerine, A slurry was prepared'from the above. materials and added Water by mixing the con-I v; f a e Drying temperature, 2 201 V The ;values were employed' asti-points"in-plotting{.;the curve ZSof-FIG. 2., :The: samples tested foi wett'ensile'- strength were iprepare drby soaking sections"; of "theffilm irrwater for aboutone minute whereby {they acquire" a i water content; ofabout 50% to- It willibe noted; that at 'C'. the wet strength'increasesrapidly upwarda 'ly through .C. However; sheets dried atabove 160 f" C.1w'ere jquite noticeably scorched, with;:a corresponding" manifestation 10f brittleness land somegdistintegrationfl it Fora good product, therefore, 160 FCJis indicated' as the 5 upper limit. Additional subsequent.testsi'producedwalues which fell on orivery close to the origin'alf'cur've 25.? I

Similar samples Were also't'ested fofdry'tensile strength andit; appearedithat allflsarnples: tested possessed at least a moderately. satisfactory dry tensile" strength. I However, itwas found-thatithose samples dried in accordance :with '1 ;they present :in'ventionlhad superior dry tensile, strength in; the range of considerably above lOOggrarns per squarefz .inch. 7 The s'amplcsreferredi'to: aslte'stedz for tdry tensile strength f-were first conditioned inian atmospherfof% relative humiditywhereby thecsampl'es acquiredia,'mois 5. c ture content i'nlthe,rangeof'10%"toi14%,'which"is sub stantiaIIy standard for smokin'g' tobaccoproducts; I

V Distintegrationjin Water testsijwere also rmadej One 6 inch squares of the samplesdriedfat each'temperature; were 'pl'acedvini beakers' containing ,100 ml; "of iwateny Each beaker was given the same amountjofagitation andithe time recordedpvhen the; one .injchfsqu'ares'bganc, f to disintegrate. 'Allithe samples-dried grand; below 100 C. disfinte'grated-vvithino hours; Th e samples driedabo've 100 C. and uplto 160 C..were still intact after 52j'h ou rs.

ately 5% solid tobacco mate: v rials. and 95,% water. Thelsolid tobacco material c'on- 1 Wet tensile strength," 7 v gms'pering'width Similar tests .inlyvhich the drying temperature; was-n i 160 C. and higher were also carried out. Samples of similar composition and prepared similarly when dried at temperatures above 160 C. begin to show signs of scorching and at temperatures substantially above 160 C., as for example at 170 C., the scorching was distinctly apparent. Such scorching rendered the sheet very dark brown to black and made the material unattractive. In addition, such scorching altered the flavor of the tobacco. The scorched material was found to have chemical changes which had occurred during scorching. These changes included the transformation of the sugars normally present in the tobacco.

- Tests, generally similar to the above tests, were also run with samples prepared and treated similarly to those listed in Table A except the proportions of the stems and leaf parts and the percentage of total solids present in the slurry differed. Sheet material of adequate wet tensile strength was obtained when the film was dried at a temperature within the range of 120 C. up to 160 C. For example, in one series of tests tobacco slurries and test strips were prepared in substantially the manner described above and the test strips were wetted as described above and subjected to tensile strengths in the Scott tester in accordance with the procedure described above the drying temperature being at 140 C. In one sample (B l) the total solids content of the slurry was 4% and the layer thereof flowed onto the casting plate was approximately .075 of an inch thick. In another sample (B-Z) the total solids content of the slurry was 7% and the layer thereof flowed onto the casting plate was approximately .100

of an inch thick. In each case the solids part was composed of the following proportions:

Percent Stem pulp 50 Leaf fines 46 Glycerine 4 Total 100 The tensile strength recorded in the below Table B was determined as above described, except the final value was the average of tenor more samples.

Table B Solids Grns. per Sample Content, inch width percent B-l 4 74. 1 B-2 7 86.

In another test a slurry was similarly made having 5% total solids but the solids were in the proportions:

Percent Stem pulp 35 Leaf fines 61 Glycerine 4.

Total 100 Sheets were cast and samples C-1 and 6-2 were made employing different drying temperatures. The thicknesses of the layer of the slurry as flowed onto the casting plate was approximately .100 of an inch. The wet tensile strength as determined on the Scott tester in the manner In still another series of tests a slurry having 5% total solids but the solids were in the proportions:

Percent Stem pulp 75 Leaf fines 21 Glycerine 4 Total 100 Sheets were cast and samples D1 and D2 were made employing different drying temperatures. In these tests the thickness of the layer of the slurry as flowed onto the casting plate was approximately .125 of an inch. The wet tensile strength as determined on the Scott tester in the manner described above was as follows:

carried out on tobacco slurries made generally similar to those described above for Table A, but varying considerably therefrom in percentage of tobacco solids, it could be seen that with a solids content in the slurry below about 3%, the dried samples exhibited generally similar wet tensile strength as those of Table A but a substantial amount of the soluble solids ran out of the film prior to drying which altered undesirably the flavor of the product. On the other hand increasing the solids content of the formulation above about 8% resulted in a non-flowable mass which was difficult to cast and required casting in thicknesses of more than 0.150 of an inch and tendency of the dried sheet to crumble in normal desired handling conditions.

The product of the method of the present invention is also characterized by a reduction in the amount of alkaloids which are primarily nicotine, such reduction being evident at temperatures distinctly noticeable when the drying temperature reaches about 120 C. Also the sugar content is transformed and reduced with temperatures of 100 C. and higher and the sugar substantially disappears when the temperature reaches 120 C. The product of the present method also is more dense than when dried at lower temperatures and its burning rate is decreased.

The sheet material derived according to the present method may be cut up into sections corresponding in size to normal stemmed tobacco leaf portions and utilized similarly. The method therefore enables tobacco materials such as stems and fines to be converted into a product which may be readily manipulated and which may be shredded like ordinary tobacco leaf and utilized in a smoking product in a substantially simlar manner and having properties and characteristics generally similar to shredded tobacco leaf. The sheet material may be employed as a cigar wrapper since with the added wet strength it will not fall apart in the smokers mouth as readily.

It should be understood that various apparatus may be employed and certain changes made in some of the associated steps comprising the complete method and that accordingly the matter contained in the foregoing description should be regarded for the most part as illustrative and not in a limiting sense.

I claim:

1. A method of forming a tobacco sheet material of increased wet strength comprising preparing a slurry of finely reduced tobacco parts in water, the said tobacco parts being present in an amount in the range of 3% to 8% with a substantial proportion reduced to a gelatinous state, casting a film of said slurry on a fiat traveling supporting surface, passing the supporting surface and film 7 through a drying ,zone'having an atmosphere in the temperature range of 120": C. to 160 C.,' heating thefilrnin said drying zone until the temperature of the: film reaches the boiling'pointpf water,iwhere by the free water is removedand thereafter, heating gsaidfilm in said drying zone; until th'e t eirnperature of said film is at' least 120 C. and lessthan 160 C., passing the supporting'surface and dried film thIQugh arewetting zone Whereliquid is applied to i Wet the film to a moisturecontent in the range of. to. stripping the -,wetted film from the supportings'ur-' face, drying it to below'substantially 35% moisture content, and collecting the product.

2. A method of forming a tobacco sheet material of increased Wet str'engthcomprising preparingasiurry of finely reduced tobacco parts inlwater, the said tobacco 8% with a substantial proportion reduced to a gelatinous through a ,drying zone having an atmosphere in the tem: perature range of C: to C., heating .thefilm in anaaaee :15.) parts being present inlan amountin the-range of,3% to said drying zone; until thetemperature-of the film. reaches the boiling'point of Water; Whereby the free water is V removed and thereafter heating said film in said drying zoneuntil the temperature of said filni'is at least 130" C.

and less than 150 C., passing thesupporting surface-and V dried film through a rewetting zone Where liquid'is applied 1 to wet the film to'a moisture content inthe range of 20% f to 48%, stripping the Wetted film from the supporting surface, drying it to below substantially 35% moisture content, and ciollecting'thev product. 1 7

3. A'method of forming a tobacco sheetmaterialcoma prising preparing a slurry of'tobacco parts in'a finely regduced, state and containing a substantial proportion of V gelatinized tobacco parts in water, with the tobacco parts being present in-an amount of from about 3% 'to about; 8% by weight of the total slurry composition, casting said.

slurry'into a film, heating said film at a temperature of 'r' zit-least theboiling point ofWater-and continuingsaid heat? ing until the temperature of the fihnghas reached the boiling point of water torernoveialllof the free waterfpresent; 1 therein 7 and thereafter? heating-the 'fiim in'ganfi atmosphere which is maintained'atEatern erature of at least 120 C;

7 until the temperature or the filrn isat leastflZQ C; and less 4.1A method of forming a tobacco sheet materialicorn prising; preparing1aslurryfof tobacco :parts in a finely: reduced state: and containing a su bstantialgproportion@ofv V geiatinized :toba'cco parts 'inwater, with the i tobacco. parts r beingpresent in an-jarnount:of frozn'about 3% -to fabout-- 8% byweightfof zthe total slurry composition,castingsaid slurry intoa film, heating said'filrmat a temperature-0f at lease-the iboiling point; of water and continuing said heat- 7 ing until the temperature of: thenfilrn hasreached'the boil: V :1 ing point of watert'tojremovejallj of the ire" waterpresent ,1

' therein;andthereafter; heating the film in an atmosphere Whichfls maintainediata temperatureiofiat,least 1309 0.:

10f the filrri is'iat" 1ea'styl30 C; and

untilthe temperature less than 1 50 ?v CL; 4

' Referenceshy thegExaminer it 'VVUNITEDQYS'IATE' PATENTSQ;

FOREIGNPAT Q 5 61 fG ermax y; 1

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1. A METHOD OF FORMING A TOBACCO SHEET MATERIAL OF INCREASED WET STRENGTH COMPRISING PREPARING A SLURRY OF FINELY REDUCED TOBACCO PARTS IN WATER, THE SAID TOBACCO PARTS BEING PRESENT IN AN AMOUNT IN THE RANGE OF 3% TO 8% WITH A SUBSTANTIAL PROPORTION REDUCED TO A GELATINOUS STATE, CASTING A FILM OF SAID SLURRY ON A FLAT TRAVELING SUPPORTING SURFACE, PASSING THE SUPPORTING SURFACE AND FILM THROUGH A DRYING ZONE HAVING AN ATMOSPHERE IN THE TEMPERATURE RANGE OF 120*C. TO 160*C., HEATING THE FILM IN SAID DRYING ZONE UNTIL THE TEMPERATURE OF THE FILM REACHES THE BOILING POINT OF WATER, WHEREBY THE FREE WATER IS RE- 